Because environmental factors can influence the likelihood that a person will engage in physical activity (PA), we propose to investigate the role of community characteristics in PA levels. The research will form an ancillary study to the NHLBI-funded multi-centered Trial of Activity for Adolescent Girls (TAAG), a group (school)-randomized controlled intervention trial to increase PA among a cohort of sixth grade girls over 2.5 years. The parent TAAG study will be collecting measures of physical activity using both self-report and CSA accelerometers, small monitors worn at the hip that record acceleration and deceleration of movement without the need for any reporting from the participants. Using a radius of 5 miles around each participating TAAG school and around the homes of each study participant, we plan to use geographic information systems (GIS) to gather information documenting proximity of recreational facilities, street design, population density, population mix (ethnic/age distribution), crime, availability of mass transit, neighborhood socioeconomic status (SES), geographic elevations and topography and types of land use. Using hierarchical linear modeling, with girls nested within neighborhoods, while controlling for individual level factors such as race and socioeconomic status, we plan to investigate the relationship of the environment to individual physical activity. In addition, by following girls over time, we plan to investigate whether the effect of the TAAG intervention will be modified by community characteristics. This study will be unique in its scope of exploring the role of community environments in physical activity across six very different urban, suburban, and rural areas: San Diego, CA, Minneapolis, MN, Baltimore, MD, New Orleans, LA, Tucson, AZ and Columbia, SC.